Augmented reality is becoming increasingly common in many applications. Augmented reality refers to presentation of a live view of a physical real-world scene along with additional computer-generated images. The computer-generated images are superimposed on a user's view of the real world scene, thus providing a composite view. The computer-generated images commonly represent one or more virtual objects. The virtual objects are not tangible, and are only visible through the view of the augmented reality.
Commonly a marker is placed in the real-world scene to inform an augmented reality system of the location of a virtual object. The marker may be a two-dimensional binary pattern distinguishable from other objects in the scene. A marker can be printed on paper and attached to a physical surface. Alternatively, a marker can be projected onto a scene using an image projector. In either case, the marker becomes part of the real-world scene. As a consequence, both the virtual object and also the marker become visible in the augmented view of the scene.
One method of addressing the above is by printing the marker with infra-red ink. The marker is then captured by an augmented reality system using an additional infra-red camera. Another method prints the marker with translucent retro-reflective ink. The marker is not visible in general, and is only detectable when illuminated using an IR-LED.
Another method projects a visible marker at a high frame rate (e.g., 120 Hz) and captures the marker with a high speed camera. For every alternate frame, the method also projects a complement image of the marker. Because the human eye is not capable of seeing at very high frame rates, the marker and the complement of the marker merge into a region of flat light (i.e. a region of uniform illumination) making the marker imperceptible to an observer. The method hides the marker, but also creates an unwanted flat light region.
Another method projects a marker and the complement of the marker alternately at a high frame rate. The method constructs the marker and the complement in such a way that the two merge into a photographic image, instead of a flat light region.
Thus, a need exists for an improved method of removing a marker from a projected marker.